preproc.c: fix handling of %? and %??
preproc.c: fix handling of %? and %??

techkey/nasm,projedi/nasm,turingstudio/nasm,projedi/nasm,techkey/nasm,techkey/nasm,Distrotech/nasm,techkey/nasm,letolabs/nasm,Distrotech/nasm,letolabs/nasm,Distrotech/nasm,projedi/nasm,projedi/nasm,projedi/nasm,turingstudio/nasm,letolabs/nasm,techkey/nasm,turingstudio/nasm,turingstudio/nasm,Distrotech/nasm